1. Field of the Invention
The present invention relates to a magnetic tape drive that can provide data tracks along the width directions of the magnetic tape in the high density. Preferably, the present invention relates to a magnetic tape drive, which can provide more data tracks along the width directions of the magnetic tape.
2. Description of Relevant Art
In recent years, a high-density recording technique to be applied to a magnetic tape has been developed rapidly, and thus a magnetic tape whose recording capacity is more than 100 G bytes has been brought to the market. In these conventional magnetic tapes, the width of the data track and the interval between data tracks have been made narrow gradually in order to increase the number of data tracks, when providing data tracks on the magnetic tape.
In the conventional magnetic tape drive that performs the recording and reproducing of data to the above described magnetic tape, a head unit, which has a plurality of data signal recording heads (hereinafter indicated as “recording head”) and data signal reproducing heads (hereinafter indicated as “reproducing head”), is installed.
In this head unit, the recording (reproducing) of data on the adjacent data track is performed by the same recording head. Thus, the recording (reproducing) of data is performed by changing the data track in due order. To be more precise, when the recording (reproducing) of data by the recording head (reproducing head) is performed from one end to the other end of the data track, the position in the width direction of the head unit is shifted to just above the adjacent data track. Then, the recording (reproducing) of data by the recording head (reproducing head) is performed from the other end to one end. By repeating this motion of the recording head (reproducing head) for several times, the recording (reproducing) of data on (from) the magnetic tape is achieved.
In the conventional magnetic tape drive, therefore, a tracking servo technique that controls the position in the width directions of the head unit is adopted.
Here, the tracking servo technique is a technique that allows the head unit to track the data track. In other words, this is a technique that allows the head unit to move along the data track with accuracy. In this case, the tracking of the head unit is performed by controlling the position of the head unit along the width directions with respect to the magnetic tape using an actuator, which is operated based on the servo signal obtained by the readout of the servo signal from the magnetic tape. Here, servo signal is a signal previously recorded on the magnetic tape and is obtained using a servo signal readout head.
As examples of the tracking servo technique, a technique disclosed in Japanese unexamined patent publication H08-227511 and a technique disclosed in Japanese unexamined patent publication H08-30942 can be cited. In H08-227511, an amplitude servo method, in which servo burst patterns as a servo signal that are lined up in two lines along traveling directions of the magnetic tape are used, is disclosed. In H08-30942, a timing based servo method, in which timing based signals as a servo signal that are recorded on the magnetic tape are used, is disclosed.
In the conventional magnetic tape drive, the recording head is shifted to the next position, from which new data track is provided along the longitudinal directions of the magnetic tape, when the provision of one data track by the recording head is terminated.
In the conventional magnetic tape drive, therefore, a margin having a predetermined width is provided between adjacent data tracks so that the newly provided data track will not contact the data track provided before.
In the conventional magnetic tape drive, additionally, various kinds of efforts that is used for improving the accuracy of the tracking servo technique has been attempted in order to line up data tracks along the width directions of the magnetic tape at a short margin (interval).
As reasons described above, the magnetic tape drive that can provide data tracks along the width directions of the magnetic tape at short interval has been required.